I would be cautious with the side pack type pdf. They work, but you have to crawl in it if the need arises. If you are a good swimmer and don't panic easy, then you may be ok with one. If you get the breath knocked out of you or knocked stupid, then you could be in serious trouble.

We use the Mustsangs. We also have SoSpenders. Both are fairly comfortable, but the Mustang will keep your face out of the water (in case you get knocked stupid). In real hot weather, they both suck.